Exactly, and fees are only an incentive. There's nothing stopping miners from discarding your transaction. Therefore trust that miners won't discard your transaction is required.
Fees being an incentive == trust is a strange definition of trust. But if that's the definition you want to roll with, sure distributed currencies rely on trust.
the "only" part before "an incentive" was important. They weren't saying because the fees are an incentive there is therefore trust, but rather, that one is trusting that, essentially, that this incentive will be enough.
Of course, the concern that some particular miner might just have it out for you to a degree that outweighs this incentive, or who has some other incentive to not include your transaction, is more mitigated when there are more separate/independent miners/pools .
I don't know why they would discard a transaction. The point is that they can discard transactions, which appears to invalidate the claim that bitcoin payments are "uncensorable" and "trustless".